The major objective of this research is to obtain an understanding of the regulation of the biosynthesis of saturated fatty acids and cholesterol in the developing nervous system. Delineation of the mechanisms underlying the regulatory changes of the critical enzymes involved in these biosyntheses will be emphasized particularly. Although our work will include studies of the developing mammalian (rat) brain an increasing emphasis will be placed on cultured glial and neuronal cells to serve as more readily studied models of specific aspects of brain development. Synthesis of saturated fatty acids by the de novo and chain elongation pathways will be investigated. Immunochemical techniques will be utilized to define the mechanisms underlying the regulatory changes in enzymatic activity of the de novo pathway, acetyl-CoA carboxylase (ACC) and fatty acid synthetase (FAS). The regulatory effectors of importance in these and subsequent studies will include lipid, certain hormones, cyclic mononucleotides, certain drugs, and selected metabolites. Determinations of the synthesis and degradation of ACC during brain maturation will provide critical insight into the mechanisms underlying the developmental changes of this important enzyme. Further elucidation of the role of brain FAS in de novo fatty acid synthesis will be provided by purification and characterization of the enzyme and determination of its primer specificity. Related to the latter will be the definition of the role of the beta-reductive enzymes in regulation of de novo fatty acid synthesis during brain development and in cultured glial and neuronal cells. Regulation of cholesterol biosynthesis will be explored, particularly at the enzyme level, in developing mammalian (rat) brain and in cultured glial and neuronal cells. The proposed research should define important regulatory effectors operative in developing brain and in the cultured cells, the enzymatic sites that mediate the responses of the effectors, and the mechanisms by which the effectors exert their impact on these critical enzymes. Introductory work indicates the importance of HMG-CoA reductase as a major regulatory site. Particular emphasis will be placed on the interrelations between regulation of fatty acid and cholesterol synthesis and on additional or alternative regulatory sites, some heretofore not clearly recognized.